Development of novel whole-cell immunoadsorbents by yeast surface display of the IgG-binding domain

The ZZ domain derived from Staphylococcus aureus, which binds to the Fc par t of immunoglobulin G (IgG), was displayed on the cell surfaces of yeast Sa ccharomyces cerevisiae by cell-surface engineering using the C-terminal hal f of a-agglutinin under control of the 5'-upstream region of the isocitrate lyase gene from Candida tropicalis (UPR-ICL). Display of ZZ on the cell su rface was confirmed by immunofluorescence microscopy. Enzyme-linked immunos orbent assay (ELISA) and sandwich ELISA using the S. cerevisiae cells displ aying ZZ detected IgG and antigen (human serum albumin) down to a concentra tion of 1-10 ng/ml in both cases. The detection range covered by these assa y systems was wide and could be varied by adjusting the amount of cells and reaction times with horseradish peroxidase (HRP) substrate. Moreover, yeas t cells displaying ZZ were successfully used for repeated affinity purifica tion of IgG from serum. These results indicate that S. cerevisiae displayin g ZZ may constitute novel and genetically renewable whole-cell immunoadsorb ents widely applicable to immunoassays and affinity purification.